Elastomeric polymer films have found widespread use in a number of applications because of the desirable elongation and retraction properties they exhibit. For example, elastomeric films have been laminated to inelastic materials such as nonwoven webs to form elastic composites that are used in garment materials, pads, diapers, training pants, swimwear, adult incontinence products and feminine care products. One class of elastomeric polymers often chosen for use in these applications includes styrene copolymers. However, these elastomeric polymers, in their pure form, are expensive and are only available from a limited number of suppliers. In order to reduce costs while retaining the desired level of elasticity, many manufacturers have resorted to using elastomeric films including blends of elastomeric polymer with other less expensive and/or less elastic materials.
Typically, these blended elastomeric films are formed through dry blending the elastomeric polymers with the less expensive and/or less elastic materials prior to extruding, blowing or casting the film. An example of an elastomeric polymer dry-blended with a less elastic material is disclosed in, for example, commonly assigned U.S. Pat. No. 4,663,220 to Wisneski et al., which is hereby incorporated by reference.
Alternatively, some manufacturers have elected to use elastomeric films that include two or more layers of material having varying levels of elasticity that are laminated together. In this case, each layer would be formed separately then brought together and laminated. The layers are typically adhered to each other by adhesive bonding, thermal bonding, point bonding, ultrasonic welding or the like. While these laminated elastomeric films may be less expensive in terms of raw materials, additional costs are expended in the formation of separate sheets of material and in conducting the lamination process.
With the foregoing in mind, there is a need or desire for an elastomeric film that exhibits many of the elastic properties such as set, hysteresis and stress relaxation at body temperature of comparable dry-blended and extruded or laminated films.
It is a feature and advantage of the invention to provide an elastomeric film that is less expensive to produce. It also a feature and advantage of the invention to provide an elastomeric film that includes a pure elastomeric polymer and a less expensive and/or less elastic material that is easier to produce and does not involve a difficult and/or detrimental dry blending procedure or an additional lamination process.
It is a further feature and advantage of the invention to provide a composite including an inelastic material such as an extensible nonwoven web and an elastomeric film that is less expensive and easier to produce.